EP1073756A4 - IDENTIFICATION OF A cDNA ASSOCIATED WITH ISCHEMIA IN HUMAN HEART TISSUE - Google Patents

Abstract

A new gene that is up-regulated in ischemic heart tissue is described. Also described are nucleic acid molecules that contain the new gene. These nucleic acid molecules may be operably linked to one or more expression control elements to produce, for example, a vector for transforming host cells. By culturing such host cells under proper conditions, protein from the new gene may be expressed and purified.

Description

IDENTIFICATION OF A cDNA ASSOCIATED WITH ISCHEMIA IN HUMAN

HEART TISSUE

FIELD OF THE INVENTION

The invention relates generally to the changes in gene expression in ischemic heart tissue compared to normal human heart tissue. The invention relates specifically to a novel human gene which is up-regulated in ischemic human heart tissue. This application is related to U.S. Provisional Application Serial No. 60/079,377, filed March 26, 1998, which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Cardiovascular disease is a general diagnostic category consisting of several separate diseases. Coronary heart disease and cerebrovascular disease are major components of cardiovascular disease with 478,530 dying of coronary heart disease and 144,070 dying of cerebrovascular disease in the U.S. in 1991. See Cecil Textbook of Medicine, Bennet and Plum Eds., W.B. Saunders Co., 1996. Many of the acute forms of coronary heart disease are caused by coronary artery abnormalities such as coronary atherosclerosis. Among the more common causes and contributing factors in sudden cardiac death are chronic ischemic heart disease and ischemic cardiomyopathy.

Chronic ischemic heart disease and ischemic cardiomyopathy are caused in part by episodes of insufficient myocardial oxygen supply. Myocardial oxygen supply is governed by coronary blood flow and the ability of the myocardium to extract oxygen from the blood delivered to it. Unlike other organs, the heart always extracts oxygen with near maximal efficiency from the blood. Even under situations of minimal demand, there is little potential for enhanced oxygen extraction to counter increased oxygen demands. Coronary blood flow, on the other hand, can increase several-fold in normal subjects as a result of coronary arterial vasodilation. Coronary arterial vasodilation is regulated by the coronary endothelium which releases vasodilatory substances, most importantly nitric oxide.

In atherosclerotic coronary heart disease, endothelial dysfunction may diminish - 2 - production of vasodilatory substances, such as nitric oxide. Myocardial ischemia results when autoregulatory vasodilation is prevented, whether by flow-limiting coronary arterial stenosis or by endothelial dysfunction. In both cases, arterial blood flow can no longer increase proportional to rising oxygen demands. In other situations, myocardial ischemia may occur when oxygen demands are constant but there is a primary decrease in coronary blood flow mediated via coronary artery spasm, rapid evolution of the underlying atherosclerotic plaque leading to a reduced coronary arterial lumen caliber, and/or intermittent microvascular plugging by platelet aggregates.

At the molecular level, ischemia is characterized by the differential expression of numerous genes compared to normal heart tissue. For instance, in human heart failure caused by ischemic cardiomyopathy, expression of the β,- and β₂-adrenergic receptors of the adenyl cyclase signal transduction system is impaired by reductions in the expression of mRNA for each receptor (Ihl-Vahl et al, 1996, J. Mol. Cell. Cardiol. 28:1-10). Ischemic injury is also known to lead to the differential expression of heat shock and immediate early genes such as hsplO, c-fos, c-jun,jun- as well the genes encoding angiotensin receptor subtypes (Plumier et α/., 1996, J. Mol. Cell. Cardiol. 28:1251-1260; Wharton et al., 1998, J. Pharmoc. Experiment. Therap. 284(1) 323-336; and Heads et al. 1995, J. Mol. Cell. Cardiol. 27:2133-2148).

The identification of new genes that are differentially expressed in ischemic heart tissue will allow for the development of numerous diagnostic and therapeutic applications such as molecular probes and new agents which modulate the activity or expression of these genes.

SUMMARY OF THE INVENTION The present invention is based on our discovery of a new gene which is up- regulated in ischemic heart tissue. The invention includes isolated nucleic acid molecules selected from the group consisting of an isolated nucleic acid molecule that encodes the amino acid sequence of SEQ ID No.2, an isolated nucleic acid molecule that encodes a fragment of at least 10 amino acids of SEQ ID No.2, an isolated nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ ID No. 1 under conditions of sufficient stringency to produce a clear signal and an isolated nucleic acid molecule which hybridizes to a nucleic acid molecule that encodes the amino acid sequence of SEQ ID No. - 3 -

2 under conditions of sufficient stringency to produce a clear signal.

The present invention further includes the nucleic acid molecules operably linked to one or more expression control elements, including a vector comprising the isolated nucleic acid molecules. The invention further includes host cells transformed to contain the nucleic acid molecules of the invention and methods for producing a protein comprising the step of culturing a host cell transformed with the nucleic acid molecule of the invention under conditions in which the protein is expressed.

The invention further provides an isolated polypeptide selected from the group consisting of an isolated polypeptide comprising the amino acid sequence of SEQ ID No.2, an isolated polypeptide comprising a fragment of at least 10 amino acids of SEQ ID No.2, an isolated polypeptide comprising conservative amino acid substitutions of SEQ ID No.2 and naturally occurring amino acid sequence variants of SEQ ID No.2.

The invention further provides an isolated antibody that binds to a polypeptide of the invention, including monoconal and polyclonal antibodies. The invention further provides methods of identifying an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2 comprising the steps of exposing cells which express the nucleic acid to the agent and determining whether the agent modulates expression of said nucleic acid, thereby identifying an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2.

The invention further provides methods of identifying an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2 comprising the steps of exposing cells which express the protein to the agent and determining whether the agent modulates at least on activity of said protein, thereby identifying an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2.

The invention further provides methods of identifying binding partners for a protein comprising the sequence of SEQ ID No. 2, comprising the steps of exposing said protein to a potential binding partner and determining if the potential binding partner binds to said protein, thereby identifying binding partners for a protein comprising the sequence of SEQ ID No. 2

The present invention further provides methods of modulating the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2 comprising the step - 4 - of administering an effective amount of an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2. The invention also provides methods of modulating at least one activity of a protein comprising the sequence of SEQ ID No.2 comprising the step of administering an effective amount of an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 Figure 1 is a section of an autoradiograph of the expression profile generated from cDNAs made with RNA isolated from ischemic and control, non-ischemic heart tissue.

Figure 2 Figure 2 shows the potential binding, phosphorylation and enzymatic sites of the protein of SEQ ID No.2.

Figure 3 Figure 3 is a Northern blot of RNA isolated from various tissues. Figure 4 Figure 4 is a PCR-expression analysis of RNA isolated from various tissues.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT I. General Description The present invention is based in part on identifying a new gene that is differentially regulated or expressed in human ischemic heart tissue compared to normal human heart tissue. This gene, which may be distantly related to human myosin light chain kinases, encodes a protein predicted to consist of 819 amino acids.

The protein can serve as a target for agents that can be used to modulate the expression or activity of the protein. For example, agents may be identified which modulate biological processes associated with ischemic injury to the heart such as chronic ischemic heart disease and ischemic cardiomyopathy. Agents may also be identified which modulate the biological processes associated with recovery to ischemic injury to the heart. The present invention is further based on the development of methods for isolating binding partners that bind to the protein. Probes based on the protein are used as capture probes to isolate potential binding partners, such as other proteins. Dominant negative - 5 - proteins, DNAs encoding these proteins, antibodies to these proteins, peptide fragments of these proteins or mimics of these proteins may be introduced into cells to affect function. Additionally, these proteins provide a novel target for screening of synthetic small molecules and combinatorial or naturally occurring compound libraries to discover novel therapeutics to regulate heart function.

II. Specific Embodiments

A. The Protein Associated with Ischemic Heart Tissue

The present invention provides isolated protein, allelic variants of the protein, and conservative amino acid substitutions of the protein. As used herein, the protein or polypeptide refers to a protein that has the human amino acid sequence of that depicted in SEQ ID No.2. The invention includes naturally occurring allelic variants and proteins that have a slightly different amino acid sequence than that specifically recited above. Allelic variants, though possessing a slightly different amino acid sequence than those recited above, will still have the same or similar biological functions associated with the 819 amino acid protein.

As used herein, the family of proteins related to the 819 amino acid protein refer to proteins that have been isolated from organisms in addition to humans. The methods used to identify and isolate other members of the family of proteins related to the 819 amino acid protein are described below.

The proteins of the present invention are preferably in isolated form. As used herein, a protein is said to be isolated when physical, mechanical or chemical methods are employed to remove the protein from cellular constituents that are normally associated with the protein. A skilled artisan can readily employ standard purification methods to obtain an isolated protein.

The proteins of the present invention further include conservative variants of the proteins herein described. As used herein, a conservative variant refers to alterations in the amino acid sequence that do not adversely affect the biological functions of the protein. A substitution, insertion or deletion is said to adversely affect the protein when the altered sequence prevents or disrupts a biological function associated with the protein. For example, the overall charge, structure or hydrophobic/hydrophilic properties of the protein can be altered without adversely affecting a biological activity. Accordingly, the amino - 6 - acid sequence can be altered, for example, to render the peptide more hydrophobic or more hydrophilic, without adversely affecting the biological activities of the protein.

Ordinarily, the allelic variants, the conservative substitution variants, the members of the protein family, will have an amino acid sequence having at least 75% amino acid sequence identity with the human sequence set forth in SEQ ID No.2, more preferably at least 80%, even more preferably at least 90%, and most preferably at least 95%. Identity or homology with respect to such sequences is defined herein as the percentage of amino acid residues in the candidate sequence that are identical with the known peptides, after aligning the sequences and introducing gaps, if necessary, to achieve the maximum percent homology, and not considering any conservative substitutions as part of the sequence identity. N-terminal, C-terminal or internal extensions, deletions, or insertions into the peptide sequence shall not be construed as affecting homology.

Thus, the proteins of the present invention include molecules having the amino acid sequence disclosed in SEQ ID No.2; fragments thereof having a consecutive sequence of at least about 3, 5, 10 or 15 amino acid residues of the 819 amino acid protein; amino acid sequence variants of such sequence wherein an amino acid residue has been inserted N- or C-terminal to, or within, the disclosed sequence; and amino acid sequence variants of the disclosed sequence, or their fragments as defined above, that have been substituted by another residue. Contemplated variants further include those containing predetermined mutations by, e.g., homologous recombination, site-directed or PCR mutagenesis, and the corresponding proteins of other animal species, including but not limited to rabbit, rat, murine, porcine, bovine, ovine, equine and non-human primate species, and the alleles or other naturally occurring variants of the family of proteins; and derivatives wherein the protein has been covalently modified by substitution, chemical, enzymatic, or other appropriate means with a moiety other than a naturally occurring amino acid (for example a detectable moiety such as an enzyme or radioisotope).

As described below, members of the family of proteins can be used: 1) to identify agents which modulate at least one activity of the protein, including agents which may modulate phosphorylation mediated by the protein, 2) in methods of identifying binding partners for the protein, 3) as an antigen to raise polyclonal or monoclonal antibodies, and 4) as a therapeutic agent. - 7 -

B. Nucleic Acid Molecules

The present invention further provides nucleic acid molecules that encode the protein having SEQ ID No.2 and the related proteins herein described, preferably in isolated form. As used herein, "nucleic acid" is defined as RNA or DNA that encodes a peptide as defined above, or is complementary to nucleic acid sequence encoding such peptides, or hybridizes to such nucleic acid and remains stably bound to it under appropriate stringency conditions, or encodes a polypeptide sharing at least 75% sequence identity, preferably at least 80%, and more preferably at least 85%, with the peptide sequences. Specifically contemplated are genomic DNA, cDNA, mRNA and antisense molecules, as well as nucleic acids based on alternative backbone or including alternative bases whether derived from natural sources or synthesized. Such hybridizing or complementary nucleic acids, however, are defined further as being novel and unobvious over any prior art nucleic acid including that which encodes, hybridizes under appropriate stringency conditions, or is complementary to nucleic acid encoding a protein according to the present invention.

"Stringent conditions" are those that (1) employ low ionic strength and high temperature for washing, for example, 0.015M NaCl/0.0015M sodium titrate/0.1% SDS at 50°C, or (2) employ during hybridization a denaturing agent such as formamide, for example, 50% (vol/vol) formamide with 0.1 % bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75 mM sodium citrate at 42°C. Another example is use of 50% formamide, 5 x SSC (0.75M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1 % sodium pyrophosphate, 5 x Denhardt's solution, sonicated salmon sperm DNA (50 μg/ml), 0.1 % SDS, and 10% dextran sulfate at 42°C, with washes at 42°C. in 0.2 x SSC and 0.1% SDS. A skilled artisan can readily determine and vary the stringency conditions appropriately to obtain a clear and detectable hybridization signal.

As used herein, a nucleic acid molecule is said to be "isolated" when the nucleic acid molecule is substantially separated from contaminant nucleic acid encoding other polypeptides from the source of nucleic acid. The present invention further provides fragments of the encoding nucleic acid molecule. As used herein, a fragment of an encoding nucleic acid molecule refers to a small portion of the entire protein encoding sequence. The size of the fragment will be determined - 8 - by the intended use. For example, if the fragment is chosen so as to encode an active portion of the protein, the fragment will need to be large enough to encode the functional region(s) of the protein. If the fragment is to be used as a nucleic acid probe or PCR primer, then the fragment length is chosen so as to obtain a relatively small number of false positives during probing/priming.

Fragments of the encoding nucleic acid molecules of the present invention (i.e., synthetic ohgonucleotides) that are used as probes or specific primers for the polymerase chain reaction (PCR), or to synthesize gene sequences encoding proteins of the invention can easily be synthesized by chemical techniques, for example, the phosphotriester method of Matteucci et al, (J Am. Chem. Soc. 103:3185-3191, 1981) or using automated synthesis methods. In addition, larger DNA segments can readily be prepared by well known methods, such as synthesis of a group of ohgonucleotides that define various modular segments of the gene, followed by ligation of ohgonucleotides to build the complete modified gene.

The encoding nucleic acid molecules of the present invention may further be modified so as to contain a detectable label for diagnostic and probe purposes. A variety of such labels are known in the art and can readily be employed with the encoding molecules herein described. Suitable labels include, but are not limited to, biotin, radiolabeled nucleotides and the like. A skilled artisan can employ any of the art known labels to obtain a labeled encoding nucleic acid molecule. Modifications to the primary structure itself by deletion, addition, or alteration of the amino acids incorporated into the protein sequence during translation can be made without destroying the activity of the protein. Such substitutions or other alterations result in proteins having an amino acid sequence encoded by a nucleic acid falling within the contemplated scope of the present invention.

C. Isolation of Other Related Nucleic Acid Molecules

As described above, the identification of the human nucleic acid molecule having SEQ ID No.1 allows a skilled artisan to isolate nucleic acid molecules that encode other members of the protein family in addition to the human sequence herein described. Further, the presently disclosed nucleic acid molecules allow a skilled artisan to isolate nucleic acid molecules that encode other members of the family of proteins in addition to the 819 amino acid protein having SEQ ID No.2. - 9 -

Essentially, a skilled artisan can readily use the amino acid sequence of SEQ ID No.2 to generate antibody probes to screen expression libraries prepared from appropriate cells. Typically, polyclonal antiserum from mammals such as rabbits immunized with the purified protein (as described below) or monoclonal antibodies can be used to probe a mammalian cDNA or genomic expression library, such as lambda gtll library, to obtain the appropriate coding sequence for other members of the protein family. The cloned cDNA sequence can be expressed as a fusion protein, expressed directly using its own control sequences, or expressed by constructions using control sequences appropriate to the particular host used for expression of the enzyme. Alternatively, a portion of the coding sequence herein described can be synthesized and used as a probe to retrieve DNA encoding a member of the protein family from any mammalian organism. Oligomers containing approximately 18-20 nucleotides (encoding about a 6-7 amino acid stretch) are prepared and used to screen genomic DNA or cDNA libraries to obtain hybridization under stringent conditions or conditions of sufficient stringency to eliminate an undue level of false positives.

Additionally, pairs of oligonucleotide primers can be prepared for use in a polymerase chain reaction (PCR) to selectively clone an encoding nucleic acid molecule. A PCR denature/anneal/extend cycle for using such PCR primers is well known in the art and can readily be adapted for use in isolating other encoding nucleic acid molecules.

D. rDNA molecules Containing a Nucleic Acid Molecule The present invention further provides recombinant DNA molecules (rDNAs) that contain a coding sequence. As used herein, a rDNA molecule is a DNA molecule that has been subjected to molecular manipulation in situ. Methods for generating rDNA molecules are well known in the art. See for example, Sambrook et al, Molecular Cloning (1989). In the preferred rDNA molecules, a coding DNA sequence is operably linked to expression control sequences and/or vector sequences.

The choice of vector and/or expression control sequences to which one of the protein family encoding sequences of the present invention is operably linked depends directly, as is well known in the art, on the functional properties desired, e.g., protein expression, and the host cell to be transformed. A vector contemplated by the present invention is at least capable of directing the replication or insertion into the host chromosome, and preferably also expression, - 10 - of the structural gene included in the rDNA molecule.

Expression control elements that are used for regulating the expression of an operably linked protein encoding sequence are known in the art and include, but are not limited to, inducible promoters, constitutive promoters, secretion signals, and other regulatory elements. Preferably, the inducible promoter is readily controlled, such as being responsive to a nutrient in the host cell's medium.

In one embodiment, the vector containing a coding nucleic acid molecule will include a prokaryotic replicon, i.e., a DNA sequence having the ability to direct autonomous replication and maintenance of the recombinant DNA molecule extrachromosomally in a prokaryotic host cell, such as a bacterial host cell, transformed therewith. Such replicons are well known in the art. In addition, vectors that include a prokaryotic replicon may also include a gene whose expression confers a detectable marker such as a drug resistance. Typical bacterial drug resistance genes are those that confer resistance to ampicillin or tetracycline.

Vectors that include a prokaryotic replicon can further include a prokaryotic or bacteriophage promoter capable of directing the expression (transcription and translation) of the coding gene sequences in a bacterial host cell, such as E. coli. A promoter is an expression control element formed by a DNA sequence that permits binding of RNA polymerase and transcription to occur. Promoter sequences compatible with bacterial hosts are typically provided in plasmid vectors containing convenient restriction sites for insertion of a DNA segment of the present invention. Typical of such vector plasmids are pUC8, pUC9, pBR322 and pBR329 available from Biorad Laboratories, (Richmond, CA), pPL and pKK223 available from Pharmacia, Piscataway, N. J.

Expression vectors compatible with eukaryotic cells, preferably those compatible with vertebrate cells, can also be used to form a rDNA molecules the contains a coding sequence. Eukaryotic cell expression vectors are well known in the art and are available from several commercial sources. Typically, such vectors are provided containing convenient restriction sites for insertion of the desired DNA segment. Typical of such vectors are pSVL and pKSV- 10 (Pharmacia), pBPV-l/pML2d (International Biotechnologies, Inc.), pTDTl (ATCC, #31255), the vector pCDM8 described herein, and the like eukaryotic expression vectors. Eukaryotic cell expression vectors used to construct the rDNA molecules of the present invention may further include a selectable marker that is effective in an eukaryotic cell, preferably a drug resistance selection marker. A preferred drug resistance marker is the gene - 11 - whose expression results in neomycin resistance, i.e., the neomycin phosphotransferase (neo) gene. (Southern et al, J. Mol. Anal. Genet. 1:327-341, 1982.) Alternatively, the selectable marker can be present on a separate plasmid, and the two vectors are introduced by co- transfection of the host cell, and selected by culturing in the appropriate drug for the selectable marker.

E. Host Cells Containing an Exogenously Supplied Coding Nucleic Acid Molecule

The present invention further provides host cells transformed with a nucleic acid molecule that encodes a protein of the present invention. The host cell can be either prokaryotic or eukaryotic. Eukaryotic cells useful for expression of a protein of the invention are not limited, so long as the cell line is compatible with cell culture methods and compatible with the propagation of the expression vector and expression of the gene product. Preferred eukaryotic host cells include, but are not limited to, yeast, insect and mammalian cells, preferably vertebrate cells such as those from a mouse, rat, monkey or human cell line.

Preferred eukaryotic host cells include Chinese hamster ovary (CHO) cells available from the ATCC as CCL61, NIH Swiss mouse embryo cells NIH/3T3 available from the ATCC as CRL 1658, baby hamster kidney cells (BHK), and the like eukaryotic tissue culture cell lines.

Any prokaryotic host can be used to express a rDNA molecule encoding a protein of the invention. The preferred prokaryotic host is E. coli.

Transformation of appropriate cell hosts with a rDNA molecule of the present invention is accomplished by well known methods that typically depend on the type of vector used and host system employed. With regard to transformation of prokaryotic host cells, electroporation and salt treatment methods are typically employed; see, for example, Cohen et al, Proc. Natl. Acad. Sci. USA 69:2110, 1972; and Maniatis et al, Molecular Cloning. A

Laboratory Mammal. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY (1982). With regard to transformation of vertebrate cells with vectors containing rDNAs, electroporation, cationic lipid or salt treatment methods are typically employed; see, for example, Graham et al, Virol. 52:456, 1973; Wigler et al, Proc. Natl. Acad. Sci. USA 76:1373-76, 1979. Successfully transformed cells, i.e., cells that contain a rDNA molecule of the present invention, can be identified by well known techniques including the selection for a selectable marker. For example, cells resulting from the introduction of an rDNA of the present invention - 12 - can be cloned to produce single colonies. Cells from those colonies can be harvested, lysed and their DNA content examined for the presence of the rDNA using a method such as that described by Southern, J. Mol. Biol. 98:503, 1975, or Berent et al, Biotech. 3:208, 1985 or the proteins produced from the cell assayed via an immunological method.

F. Production of Recombinant Proteins using a rDNA Molecule The present invention further provides methods for producing a protein of the invention using nucleic acid molecules herein described. In general terms, the production of a recombinant form of a protein typically involves the following steps: First, a nucleic acid molecule is obtained that encodes a protein of the invention, such as the nucleic acid molecule depicted in SEQ ID No. 1, or nucleotides 136-2592 of SEQ ID No.l. If the encoding sequence is uninterrupted by introns, it is directly suitable for expression in any host.

The nucleic acid molecule is then preferably placed in operable linkage with suitable control sequences, as described above, to form an expression unit containing the protein open reading frame. The expression unit is used to transform a suitable host and the transformed host is cultured under conditions that allow the production of the recombinant protein. Optionally the recombinant protein is isolated from the medium or from the cells; recovery and purification of the protein may not be necessary in some instances where some impurities may be tolerated.

Each of the foregoing steps can be done in a variety of ways. For example, the desired coding sequences may be obtained from genomic fragments and used directly in appropriate hosts. The construction of expression vectors that are operable in a variety of hosts is accomplished using appropriate replicons and control sequences, as set forth above. The control sequences, expression vectors, and transformation methods are dependent on the type of host cell used to express the gene and were discussed in detail earlier. Suitable restriction sites can, if not normally available, be added to the ends of the coding sequence so as to provide an excisable gene to insert into these vectors. A skilled artisan can readily adapt any host/expression system known in the art for use with the nucleic acid molecules of the invention to produce recombinant protein. - 13 -

G. Methods to Identify Binding Partners

Another embodiment of the present invention provides methods for use in isolating and identifying binding partners of proteins of the invention. In detail, a protein of the invention is mixed with a potential binding partner or an extract or fraction of a cell under conditions that allow the association of potential binding partners with the protein of the invention. After mixing, peptides, polypeptides, proteins or other molecules that have become associated with a protein of the invention are separated from the mixture. The binding partner that bound to the protein of the invention can then be removed and further analyzed. To identify and isolate a binding partner, the entire protein, for instance the entire 819 amino acid protein of SEQ ID No.2 can be used. Alternatively, a fragment of the protein can be used.

As used herein, a cellular extract refers to a preparation or fraction which is made from a lysed or disrupted cell. The preferred source of cellular extracts will be cells derived from human heart tissue, for instance, ischemic human heart tissue. Alternatively, cellular extracts may be prepared from normal human heart tissue or available cell lines, particularly heart or muscle derived cell lines.

A variety of methods can be used to obtain an extract of a cell. Cells can be disrupted using either physical or chemical disruption methods. Examples of physical disruption methods include, but are not limited to, sonication and mechanical shearing. Examples of chemical lysis methods include, but are not limited to, detergent lysis and enzyme lysis. A skilled artisan can readily adapt methods for preparing cellular extracts in order to obtain extracts for use in the present methods.

Once an extract of a cell is prepared, the extract is mixed with the protein of the invention under conditions in which association of the protein with the binding partner can occur. A variety of conditions can be used, the most prefeπed being conditions that closely resemble conditions found in the cytoplasm of a human cell. Features such as osmolarity, pH, temperature, and the concentration of cellular extract used, can be varied to optimize the association of the protein with the binding partner.

After mixing under appropriate conditions, the bound complex is separated from the mixture. A variety of techniques can be utilized to separate the mixture. For example, antibodies specific to a protein of the invention can be used to immunoprecipitate the binding partner complex. Alternatively, standard chemical separation techniques such as - 14 - chromatography and density/sediment centrifugation can be used.

After removal of nonassociated cellular constituents found in the extract, the binding partner can be dissociated from the complex using conventional methods. For example, dissociation can be accomplished by altering the salt concentration or pH of the mixture.

To aid in separating associated binding partner pairs from the mixed extract, the protein of the invention can be immobilized on a solid support. For example, the protein can be attached to a nitrocellulose matrix or acrylic beads. Attachment of the protein to a solid support aids in separating peptide/binding partner pairs from other constituents found in the extract. The identified binding partners can be either a single protein or a complex made up of two or more proteins.

Alternatively, the nucleic acid molecules of the invention can be used in a yeast two-hybrid system. The yeast two-hybrid system has been used to identify other protein partner pairs and can readily be adapted to employ the nucleic acid molecules herein described.

H. Methods to Identify Agents that Modulate the Expression a Nucleic Acid Encoding the Ischemic Heart Associated Protein

Another embodiment of the present invention provides methods for identifying agents that modulate the expression of a nucleic acid encoding a protein of the invention such as a protein having the amino acid sequence of SEQ ID No. 2. Such assays may utilize any available means of monitoring for changes in the expression level of the nucleic acids of the invention. As used herein, an agent is said to modulate the expression of a nucleic acid of the invention, for instance a nucleic acid encoding the protein having the sequence of SEQ ID No.2, if it is capable of up- or down-regulating expression of the nucleic acid in a cell.

In one assay format, cell lines that contain reporter gene fusions between the open reading frame defined by nucleotides 136-2592 of SEQ ID No.l and any assayable fusion partner may be prepared. Numerous assayable fusion partners are known and readily available including the firefly luciferase gene and the gene encoding chloramphenicol acetyltransferase (Alam et al. (1990) Anal. Biochem. 188:245-254). Cell lines containing the reporter gene fusions are then exposed to the agent to be tested under appropriate - 15 - conditions and time. Differential expression of the reporter gene between samples exposed to the agent and control samples identifies agents which modulate the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2.

Additional assay formats may be used to monitor the ability of the agent to modulate the expression of a nucleic acid encoding a protein of the invention such as the protein having SEQ ID No.2. For instance, mRNA expression may be monitored directly by hybridization to the nucleic acids of the invention. Cell lines are exposed to the agent to be tested under appropriate conditions and time and total RNA or mRNA is isolated by standard procedures such those disclosed in Sambrook et al. (Molecular Cloning: A Laboratory Manual, 2nd Ed. Clod Spring Harbor Laboratory Press, 1989).

Probes to detect differences in RNA expression levels between cells exposed to the agent and control cells may be prepared from the nucleic acids of the invention. It is preferable, but not necessary, to design probes which hybridize only with target nucleic acids under conditions of high stringency. Only highly complementary nucleic acid hybrids form under conditions of high stringency. Accordingly, the stringency of the assay conditions determines the amount of complementarity which should exist between two nucleic acid strands in order to form a hybrid. Stringency should be chosen to maximize the difference in stability between the probe:target hybrid and potential probe:non-target hybrids. Probes may be designed from the nucleic acids of the invention through methods known in the art. For instance, the G+C content of the probe and the probe length can affect probe binding to its target sequence. Methods to optimize probe specificity are commonly available in Sambrook et al. (Molecular Cloning: A Laboratory Approach, Cold Spring Harbor Press, NY, 1989) or Ausubel et al. (Current Protocols in Molecular Biology, Greene Publishing Co., NY, 1995).

Hybridization conditions are modified using known methods, such as those described by Sambrook et al. and Ausubel et al. as required for each probe. Hybridization of total cellular RNA or RNA enriched for polyA RNA can be accomplished in any available format. For instance, total cellular RNA or RNA enriched for polyA RNA can be affixed to a solid support and the solid support exposed to at least one probe comprising at least one, or part of one of the sequences of the invention under conditions in which the probe will specifically hybridize. Alternatively, nucleic acid fragments comprising at least - 16 - one, or part of one of the sequences of the invention can be affixed to a solid support, such as a porous glass wafer. The glass wafer can then be exposed to total cellular RNA or polyA RNA from a sample under conditions in which the affixed sequences will specifically hybridize. Such glass wafers and hybridization methods, such as those disclosed by Beattie (WO 95/11755), are widely available. By examining for the ability of a given probe to specifically hybridize to an RNA sample from an untreated cell population and from a cell population exposed to the agent, agents which up or down regulate the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2 are identified.

I. Methods to Identify Agents that Modulate at Least One Activity of the Ischemic Heart Associated Protein

Another embodiment of the present invention provides methods for identifying agents that modulate at least one activity of a protein of the invention such as the protein having the amino acid sequence of SEQ ID No.2. Such methods or assays may utilize any means of monitoring or detecting the desired activity.

In one format, the relative amounts of a protein of the invention between a cell population that has been exposed to the agent to be tested compared to an un-exposed control cell population may be assayed. In this format, probes such as specific antibodies are used to monitor the differential expression of the protein in the different cell populations. Cell lines or populations are exposed to the agent to be tested under appropriate conditions and time. Cellular lysates may be prepared from the exposed cell line or population and a control, unexposed cell line or population. The cellular lysates are then analyzed with the probe. Antibody probes are prepared by immunizing suitable mammalian hosts in appropriate immunization protocols using the peptides, polypeptides or proteins of the invention if they are of sufficient length, or, if desired, or if required to enhance immunogenicity, conjugated to suitable carriers. Methods for preparing immunogenic conjugates with carriers such as BSA, KLH, or other carrier proteins are well known in the art. In some circumstances, direct conjugation using, for example, carbodiimide reagents may be effective; in other instances linking reagents such as those supplied by Pierce Chemical Co., Rockford, IL, may be desirable to provide accessibility to the hapten. The - 17 - hapten peptides can be extended at either the amino or carboxy terminus with a Cys residue or interspersed with cysteine residues, for example, to facilitate linking to a carrier. Administration of the immunogens is conducted generally by injection over a suitable time period and with use of suitable adjuvants, as is generally understood in the art. During the immunization schedule, titers of antibodies are taken to determine adequacy of antibody formation.

While the polyclonal antisera produced in this way may be satisfactory for some applications, for pharmaceutical compositions, use of monoclonal preparations is preferred. Immortalized cell lines which secrete the desired monoclonal antibodies may be prepared using the standard method of Kohler and Milstein or modifications which effect immortalization of lymphocytes or spleen cells, as is generally known. The immortalized cell lines secreting the desired antibodies are screened by immunoassay in which the antigen is the peptide hapten, polypeptide or protein. When the appropriate immortalized cell culture secreting the desired antibody is identified, the cells can be cultured either in vitro or by production in ascites fluid.

The desired monoclonal antibodies are then recovered from the culture supernatant or from the ascites supernatant. Fragments of the monoclonals or the polyclonal antisera which contain the immunologically significant portion can be used as antagonists, as well as the intact antibodies. Use of immunologically reactive fragments, such as the Fab, Fab', of F(ab')₂ fragments is often preferable, especially in a therapeutic context, as these fragments are generally less immunogenic than the whole immunoglobulin.

The antibodies or fragments may also be produced, using current technology, by recombinant means. Regions that bind specifically to the desired regions of receptor can also be produced in the context of chimeras with multiple species origin. In an alternative format, a specific activity of a protein of the invention may be assayed, such as the ability of the protein to phosphorylate a substrate such as myosin. Cell lines or populations are exposed under appropriate conditions to the agent to be tested. Agents which modulate the kinase activity of the protein of the invention are identified by assaying the kinase activity of the protein from the exposed cell line or population and a control, unexposed cell line or population, thereby identifying agents which modulate the kinase activity of the protein.

Kinase assays to measure the ability of the agent to modulate the kinase activity of - 18 - a protein of the invention are widely available such as the assays disclosed by Mishima et al. (1996) J. Biochem. 119:906-913) and Michnoff et /. (1986) J. Biol. Chem. 261 :8320- 8326. Alternative assay formats include actin-myosin motility assays such as those disclosed by Kohama et al. (1996) TIPS 17:284-287 or Warrick et al. (1987) Ann. Rev. Cell. Biol. 3:379-421.

Agents that are assayed in the above method can be randomly selected or rationally selected or designed. As used herein, an agent is said to be randomly selected when the agent is chosen randomly without considering the specific sequences involved in the association of the a protein of the invention alone or with its associated substrates, binding partners, etc. An example of randomly selected agents is the use a chemical library or a peptide combinatorial library, or a growth broth of an organism.

As used herein, an agent is said to be rationally selected or designed when the agent is chosen on a nonrandom basis which takes into account the sequence of the target site and/or its conformation in connection with the agent's action. As described in the Examples, there are proposed binding sites for ATP/GTP and calmodulin as well as cAMP/cGMP kinase sites, TyrP sites and Ser/Thr kinase (catalytic) sites in the protein having SEQ ID No.2. Agents can be rationally selected or rationally designed by utilizing the peptide sequences that make up these sites. For example, a rationally selected peptide agent can be a peptide whose amino acid sequence is identical to the ATP or calmodulin binding sites or domains.

The agents of the present invention can be, as examples, peptides, small molecules, vitamin derivatives, as well as carbohydrates. A skilled artisan can readily recognize that there is no limit as to the structural nature of the agents of the present invention.

The peptide agents of the invention can be prepared using standard solid phase (or solution phase) peptide synthesis methods, as is known in the art. In addition, the DNA encoding these peptides may be synthesized using commercially available oligonucleotide synthesis instrumentation and produced recombinantly using standard recombinant production systems. The production using solid phase peptide synthesis is necessitated if non-gene-encoded amino acids are to be included. Another class of agents of the present invention are antibodies immunoreactive with critical positions of proteins of the invention. Antibody agents are obtained by immunization of suitable mammalian subjects with peptides that contain as antigenic - 19 - regions those portions of the protein intended to be targeted by the antibodies.

J. Uses for Agents that Modulate at Least One Activity of the Ischemic Heart Associated Protein As provided in the Examples, the proteins and nucleic acids of the invention, such as the protein having the amino acid sequence of SEQ ID No.l, are up-regulated in ischemic heart tissue. Agents that modulate or down-regulate the expression of the protein or agents such as agonists or antagonists of at least one activity of the protein may be used to modulate biological and pathologic processes associated with the protein's function and activity.

As used herein, a subject can be any mammal, so long as the mammal is in need of modulation of a pathological or biological process mediated by a protein of the invention. The term "mammal" is meant an individual belonging to the class Mammalia. The invention is particularly useful in the treatment of human subjects. As used herein, a biological or pathological process mediated by a protein of the invention may include binding of substrates such as ATP, GTP or calmodulin or phosphorylation of a substrate such as skeletal myosin.

Pathological processes refer to a category of biological processes which produce a deleterious effect. For example, expression or up-regulation of expression of a protein of the invention is associated with chronic ischemic heart disease and ischemic cardiomyopathy. As used herein, an agent is said to modulate a pathological process when the agent reduces the degree or severity of the process. For instance, chronic ischemic heart disease or ischemic cardiomyopathy may be prevented or disease progression modulated after an ischemic event by the administration of agents which reduce or modulate in some way the expression or at least one activity of a protein of the invention. The agents of the present invention can be provided alone, or in combination with other agents that modulate a particular pathological process. For example, an agent of the present invention can be administered in combination with anti-thrombotic agents. As used herein, two agents are said to be administered in combination when the two agents are administered simultaneously or are administered independently in a fashion such that the agents will act at the same time.

The agents of the present invention can be administered via parenteral, - 20 - subcutaneous, intravenous, intramuscular, intraperitoneal, transdermal, or buccal routes. Alternatively, or concurrently, administration may be by the oral route. The dosage administered will be dependent upon the age, health, and weight of the recipient, kind of concurrent treatment, if any, frequency of treatment, and the nature of the effect desired. The present invention further provides compositions containing one or more agents which modulate expression or at least one activity of a protein of the invention. While individual needs vary, determination of optimal ranges of effective amounts of each component is within the skill of the art. Typical dosages comprise 0.1 to 100 μg/kg body wt. The preferred dosages comprise 0.1 to 10 μg/kg body wt. The most preferred dosages comprise 0.1 to 1 μg/kg body wt.

In addition to the pharmacologically active agent, the compositions of the present invention may contain suitable pharmaceutically acceptable carriers comprising excipients and auxiliaries which facilitate processing of the active compounds into preparations which can be used pharmaceutically for delivery to the site of action. Suitable formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form, for example, water-soluble salts. In addition, suspensions of the active compounds as appropriate oily injection suspensions may be administered. Suitable lipophilic solvents or vehicles include fatty oils, for example, sesame oil, or synthetic fatty acid esters, for example, ethyl oleate or triglycerides. Aqueous injection suspensions may contain substances which increase the viscosity of the suspension include, for example, sodium carboxymethyl cellulose, sorbitol, and/or dextran. Optionally, the suspension may also contain stabilizers. Liposomes can also be used to encapsulate the agent for delivery into the cell.

The pharmaceutical formulation for systemic administration according to the invention may be formulated for enteral, parenteral or topical admimstration. Indeed, all three types of formulations may be used simultaneously to achieve systemic administration of the active ingredient.

Suitable formulations for oral administration include hard or soft gelatin capsules, pills, tablets, including coated tablets, elixirs, suspensions, syrups or inhalations and controlled release forms thereof.

In practicing the methods of this invention, the compounds of this invention may be used alone or in combination, or in combination with other therapeutic or diagnostic - 21 - agents. In certain preferred embodiments, the compounds of this invention may be coadministered along with other compounds typically prescribed for these conditions according to generally accepted medical practice, such as anticoagulant agents, thrombolytic agents, or other antithrombotics, including platelet aggregation inhibitors, tissue plasminogen activators, urokinase, prourokinase, streptokinase, heparin, aspirin, or warfarin. The compounds of this invention can be utilized in vivo, ordinarily in mammals, such as humans, sheep, horses, cattle, pigs, dogs, cats, rats and mice, or in vitro.

K. Transgenic Animals Transgenic animals containing a mutant, knock-out or modified gene corresponding to the cDNA sequence of SEQ ID No.l or a construct to modify the expression level of the gene, for instance for up-regulating the expression, are also included in the invention. Transgenic animals are genetically modified animals into which recombinant, exogenous or cloned genetic material has been experimentally transferred. Such genetic material is often referred to as a "transgene". The nucleic acid sequence of the transgene, in this case a form of SEQ ID No.1 , may be integrated either at a locus of a genome where that particular nucleic acid sequence is not otherwise normally found or at the normal locus for the transgene. The transgene may consist of nucleic acid sequences derived from the genome of the same species or of a different species than the species of the target animal.

The term "germ cell line transgenic animal" refers to a transgenic animal in which the genetic alteration or genetic information was introduced into a germ line cell, thereby conferring the ability of the transgenic animal to transfer the genetic information to offspring. If such offspring in fact possess some or all of that alteration or genetic information, then they too are transgenic animals.

The alteration or genetic information may be foreign to the species of animal to which the recipient belongs, foreign only to the particular individual recipient, or may be genetic information already possessed by the recipient. In the last case, the altered or introduced gene may be expressed differently than the native gene. Transgenic animals can be produced by a variety of different methods including transfection, electroporation, microinjection, gene targeting in embryonic stem cells and recombinant viral and retroviral infection (see, e.g., U.S. Patent No. 4,736,866; U.S. Patent - 22 -

No. 5,602,307; Mullins et al. (1993) Hypertension 22(4):630-633; Brenin et al. (1997) Surg. Oncol. 6(2)99-110; Tuan (ed.), Recombinant Gene Expression Protocols, Methods in Molecular Biology No. 62, Humana Press (1997)).

A number of recombinant or transgenic mice have been produced, including those which express an activated oncogene sequence (U.S. Patent No. 4,736,866); express simian SV 40 T-antigen (U.S. Patent No. 5,728,915); lack the expression of interferon regulatory factor 1 (IRF-1) (U.S. Patent No. 5,731,490); exhibit dopaminergic dysfunction (U.S. Patent No. 5,723,719); express at least one human gene which participates in blood pressure control (U.S. Patent No. 5,731,489); display greater similarity to the conditions existing in naturally occurring Alzheimer's disease (U.S. Patent No. 5,720,936); have a reduced capacity to mediate cellular adhesion (U.S. Patent No. 5,602,307); possess a bovine growth hormone gene (Clutter et al. (1996) Genetics 143(4):1753-1760); or, are capable of generating a fully human antibody response (McCarthy (1997) The Lancet 349(9049):405). While mice and rats remain the animals of choice for most transgenic experimentation, in some instances it is preferable or even necessary to use alternative animal species. Transgenic procedures have been successfully utilized in a variety of non- murine animals, including sheep, goats, pigs, dogs, cats, monkeys, chimpanzees, hamsters, rabbits, cows and guinea pigs (see, e.g., Kim et al. (1997) Mol. Reprod. Dev. 46(4) :515- 526; Houdebine (1995) Reprod. Nutr. Dev. 35(6):609-617; Petters (1994) Reprod. Fertil. Dev. 6(5):643-645; Schnieke et al. (1997) Science 278(5346):2130-2133; and Amoah (1997) J. Animal Science 75(2):578-585).

The method of introduction of nucleic acid fragments into recombination competent mammalian cells can be by any method which favors co-transformation of multiple nucleic acid molecules. Detailed procedures for producing transgenic animals are readily available to one skilled in the art, including the disclosures in U.S. Patent No. 5,489,743 and U.S. Patent No. 5,602,307.

Without further description, it is believed that one of ordinary skill in the art can, using the preceding description and the following illustrative examples, make and utilize the compounds of the present invention and practice the claimed methods. The following working examples therefore, specifically point out prefeπed embodiments of the present invention, and are not to be construed as limiting in any way the remainder of the - 23 - disclosure.

EXAMPLES

Example 1 Identification of Differentially Expressed Ischemic Heart mRNA

Heart tissue was obtained from five male patients with inotrope-dependent post- ischemic cardiomyopathy exhibiting severe myocyte and or cardiac hypertrophy with at least three years since their first myocardial infarction. Heart tissue was also obtained from 5 female patients with idiopathic dilated cardiomyopathy exhibiting severe myocyte and/or cardiac hypertrophy and CHF duration of at least 2 years.

Total cellular RNA was prepared from the heart tissue described above as well as from control, non-ischemic heart tissue using the procedure of Newburger et al. (1981) J. Biol. Chem. 266(24): 16171-7 and Newburger et al. (1988) Proc. Natl. Acad. Sci. USA 85:5215-5219. Synthesis of cDNA was performed as previously described by Prashar et al. in

WO 97/05286 and in Prashar et al. (1996) Proc. Natl. Acad. Sci. USA 93:659-663. Briefly, cDNA was synthesized according to the protocol described in the GIBCO/BRL kit for cDNA synthesis. The reaction mixture for first-strand synthesis included 6 μg of total RNA, and 200 ng of a mixture of 1-base anchored oligo(dT) primers with all three possible anchored bases

(ACGTAATACGACTCACTATAGGGCGAATTGGGTCGACTTTTTTTTTTTTTTTTT nl wherein nl=A/C or G) (SEQ ID No.3) along with other components for first-strand synthesis reaction except reverse transcriptase. This mixture was incubated at 65°C for 5m, chilled on ice and the process repeated. Alternatively, the reaction mixture may include lOμg of total RNA, and 2 pmol of 1 of the 2-base anchored oligo(dT) primers a heel such as RP5.0 (CTCTCAAGGATCTTACCGCTT₁₈AT) (SEQ ID No.4), or RP6.0 (TAATACCGCGCCACATAGCAT₁₈CG) (SEQ ID No.5), or RP9.2 (CAGGGTAGACGACGCTACGCT₁₈GA) (SEQ ID No.6) along with other components for first-strand synthesis reaction except reverse transcriptase. This mixture was then layered with mineral oil and incubated at 65 °C for 7 min followed by 50°C for another 7 min. At this stage, 2μl of Superscript reverse transcriptase (200 units/μl; GIBCO/BRL) was added quickly and mixed, and the reaction continued for 1 hr at 45-50°C. Second- - 24 - strand synthesis was performed at 16°C for 2 hr. At the end of the reaction, the cDNAs were precipitated with ethanol and the yield of cDNA was calculated. In our experiments, -200 ng of cDNA was obtained from lOμg of total RNA. The adapter oligonucleotide sequences were Al (TAGCGTCCGGCGCAGCGACGGCCAG) (SEQ ID No.7) and

A2 (GATCCTGGCCGTCGGCTGTCTGTCGGCGC) (SEQ ID No.8). One microgram of oligonucleotide A2 was first phosphorylated at the 5' end using T4 polynucleotide kinase (PNK). After phosphorylation, PNK was heated denatured, and lμg of the oligonucleotide Al was added along with 10* annealing buffer (1 M NaCl/100 mM Tris-HCl, pH8.0/10 mM EDTA, pH8.0) in a final vol of 20 μl. This mixture was then heated at 65 °C for 10 min followed by slow cooling to room temperature for 30 min, resulting in formation of the Y adapter at a final concentration of 100 ng/μl. About 20 ng of the cDNA was digested with 4 units of Bgl II in a final vol of 10 μl for 30 min at 37°C. Two microliters (~4 ng of digested cDNA) of this reaction mixture was then used for ligation to 100 ng (~ 50-fold) of the Y-shaped adapter in a final vol of 5μl for 16 hr at 15 °C. After ligation, the reaction mixture was diluted with water to a final vol of 80 μl (adapter ligated cDNA concentration, ~50 pg/μl) and heated at 65 °C for 10 min to denature T4 DNA ligase, and 2-μl aliquots (with ~ 100 pg of cDNA) were used for PCR. The following sets of primers were used for PCR amplification of the adapter ligated 3' -end cDNAs:

TGAAGCCGAGACGTCGGTCG(T)₁₈ nl, n2 (wherein nl, n2 = AA, AC, AG AT CA CC CG CT GA GC GG and GT) (SEQ ID No.9) as the 3' primer with Al as the 5' primer or alternatively RP 5.0, RP 6.0, or RP 9.2 used as 3' primers with primer Al.l serving as the 5' primer. To detect the PCR products on the display gel, 24 pmol of oligonucleotide Al or Al.l was 5' -end-labeled using 15 μl of [γ-³² PJATP (Amersham; 3000 Ci/mmol) and PNK in a final volume of 20 μl for 30 min at 37°C. After heat denaturing PNK at 65 °C for 20 min, the labeled oligonucleotide was diluted to a final concentration of 2 μM in 80 μl with unlabeled oligonucleotide Al.l. The PCR mixture (20μl) consisted of 2 μl (« 100 pg) of the template, 2μl of 10x PCR buffer (100 mM Tris-HCl, pH 8.3/500 mM KC1), 2 μl of 15 mM MgCl₂ to yield 1.5 mM final Mg²⁺ concentration optimum in the reaction mixture, 200 μM dNTPs, 200 nM each 5' and 3' PCR primers, and 1 unit of Amplitaq Gold. Primers and dNTPs were added after - 25 - preheating the reaction mixture containing the rest of the components at 85 °C. This "hot start" PCR was done to avoid artefactual amplification arising out of arbitrary annealing of PCR primers at lower temperature during transition from room temperature to 94 °C in the first PCR cycle. PCR consisted of 5 cycles of 94 °C for 30 sec, 55 °C for 2 min, and 72 °C for 60 sec followed by 25 cycles of 94°C for 30 sec, 60°C for 2 min, and 72°C for 60 sec. A higher number of cycles resulted in smeary gel patterns. PCR products (2.5μl) were analyzed on 6% polyacrylamide sequencing gel. For double or multiple digestion following adapter ligation, 13.2 μl of the ligated cDNA sample was digested with a secondary restriction enzyme(s) in a final vol of 20 μl. From this solution, 3μl was used as template for PCR. This template vol of 3 μl carried ~ 100 pg of the cDNA and 10 mM MgCl₂ (from the 10x enzyme buffer), which diluted to the optimum of 1.5 mM in the final PCR vol of 20 μl. Since Mg²⁺ comes from the restriction enzyme buffer, it was not included in the reaction mixture when amplifying secondarily cut cDNA. Individual cDNA fragments corresponding to mRNA species were separated by denaturing polyacrylamide gel electrophoresis and visualized by autoradiography. Bands were extracted from the display gels as described by Liang et al. (1995 Curr. Opin. Immunol. 7:274-280), reamplified using the 5' and 3' primers, and subcloned into pCR-Script with high efficiency using the PCR-Script cloning kit from Stratagene. Plasmids were sequenced by cycle sequencing on an ABI automated sequencer. Alternatively, bands were extracted (cored) from the display gels, PCR amplified and sequenced directly without subcloning.

Figure 1 presents a section of an autoradiogram of the expression profile generated from cDNAs made from RNA isolated from control and ischemic heart tissue. Ci-25 is a band that corresponds to a cDNA derived from a mRNA species that is up- regulated in ischemic heart tissue in a female patient with idiopathic dilated cardiomyopathy exhibiting severe myocyte and/or cardiac hypertrophy and CHF duration of at least 2 years. The band corresponding to Ci-25 was sequenced. The sequence of CI- 25 is: GGCTCACATCTGTAATCCCAGCACTTTGGGAGGCCAAGGTGGGCAGATTGCTG GCCAACATGGTAAAACCCCATCTCTAAAGATATAAAAATTAGCTGGGCGTGGT GGCGCATACCTGTAATCCCAGCTACTTGGGAGGCTAAGGCACAAGAATCACTT AAACAGGAGGCGGGGGTTGCAGTGAGCTGAGATCACACCACTGCACTCCAGC - 26 -

CTGGGTGGCAGAGCAAAACTTTGTCCCCACCCCTGACAAAAAACAAACAAAC AAACAAAACAAAAAAAAACCTGTCAATTCA (SEQ ID No.10).

Example 2 Cloning of a Full Length cDNA Corresponding to Ci-25

The full length cDNA corresponding to Ci-25 band was obtained by the oligo-pulling method. Briefly, a gene-specific oligo was designed based on cDNA fragment Ci-25. The oligo was labeled with biotin and used to hybridize with 2 ug of single strand plasmid DNA (cDNA recombinants) from a human heart cDNA library following the procedures of Sambrook et al.. The hybridized cDNAs were separated by streptavidin-conjugated beads and eluted by heating. The eluted cDNA was converted to double strand plasmid DNA and used to transform E. coli cells (DH10B) and the longest cDNA was screened. After confirmed by PCR using gene-specific primers, the cDNA clone was subjected to DNA sequencing. The nucleotide sequence of the full-length cDNA corresponding to the differentially regulated Ci-25 band is set forth in SEQ ID No.l. The cDNA comprises 5532 base pairs with an open reading frame encoding a protein predicted to contain 819 amino acids. The predicted amino acid sequence is presented in SEQ ID Nos. 1 and 2. Comparison of the open reading to the sequences of known proteins and genes indicates that the gene may be distantly related to a known yosin light chain kinase gene as it exhibits 61% identity to a myosin light chain kinase at the nucleotide sequence level.

Example 3 Northern Blot and PCR Expression Analysis The tissue distribution of RNA encoding the differentially regulated gene encoding the protein of SEQ ID NO.2 was analyzed by Northern Blot as well as PCR expression analysis of RNA isolated from various tissues. RNA was isolated from human heart, brain, placenta, lung, liver, skeletal muscle, kidney, leukocytes, testis and pancreas using standard procedures. Northern blots were prepared using a probe derived from SEQ ID No.1 with hybridization conditions as described by Sambrook et al. PCR expression analysis was also performed using primers derived from SEQ ID No.l using AmpliTaq Gold PCR amplification kits (Perkin Elmer). Figure 3 is a Northern blot demonstrating the - 27 - presence of specific RNA in heart and skeletal muscle. Figure 4 is a PCR expression analysis demonstrating the presence of specific RNA in heart and testis.

Example 4 Generation of Transgenic Mice

Transgenic mice were generated using a gene corresponding to the cDNA sequence of SEQ ID No.1. Briefly, a cDNA fragment encoding the protein of SEQ ID No.2 was cloned into an alpha-MHC vector using standard techniques. The vector was then used to produce transgenic mice in accordance with standard techniques. Of the 22 resulting mice, six were confirmed by Southern blot to be transgene positive.

Although the present invention has been described in detail with reference to the examples above, it is understood that various modifications can be made without departing from the spirit of the invention. Accordingly, the invention is limited only by the following claims. All cited patents and publications referred to in this application are herein incorporated by reference in their entirety.

Claims

- 28 -

WHAT IS CLAIMED:

1. An isolated nucleic acid molecule selected from the group consisting of an isolated nucleic acid molecule that encodes the amino acid sequence of SEQ ID No.2, an isolated nucleic acid molecule that encodes a fragment of at last 10 amino acids of SEQ ID No.2, an isolated nucleic acid molecule which hybridizes to a nucleic acid molecule comprising SEQ ID No. 1 under conditions of sufficient stringency to produce a clear signal and an isolated nucleic acid molecule which hybridizes to a nucleic acid molecule that encodes the amino acid sequence of SEQ ID No. 2 under conditions of sufficient stringency to produce a clear signal.

2. The isolated nucleic acid molecule of claim 1, wherein the nucleic acid molecule comprises the sequence of SEQ ID No.l.

3. The isolated nucleic acid molecule of claim 2, wherein the nucleic acid molecule consists of the sequence of SEQ ID No.l.

4. The isolated nucleic acid molecule of claim 1, wherein the nucleic acid molecule comprises nucleotides 136 to 2592 of SEQ ID No.l.

5. The isolated nucleic acid molecule of claim 2, wherein the nucleic acid molecule consists of nucleotides 136 to 2592 of SEQ ID No.l.

6. The isolated nucleic acid molecule of any one of claims 1-5, wherein said nucleic acid molecule is operably linked to one or more expression control elements.

7. A vector comprising an isolated nucleic acid molecule of any one of claims 1 -5.

8. A host cell transformed to contain the nucleic acid molecule of any one claims 1-5.

9. A host cell comprising a vector of claim 7. - 29 -

10. A host cell of claim 9, wherein said host is selected from the group consisting of prokaryotic hosts and eukaryotic hosts.

11. A method for producing a protein comprising the step of culturing a host cell transformed with the nucleic acid molecule of any one of claims 1-5 under conditions in which the protein is expressed.

12. The method of claim 11, wherein said host cell is selected from the group consisting of prokaryotic hosts and eukaryotic hosts.

13. An isolated polypeptide produced by the method of claim 11.

14. An isolated polypeptide selected from the group consisting of an isolated polypeptide comprising the amino acid sequence of SEQ ID No.2, an isolated polypeptide comprising a fragment of at least 10 amino acids of SEQ ID No.2, an isolated polypeptide comprising conservative amino acid substitutions of SEQ ID No.2 and naturally occurring amino acid sequence variants of SEQ ID No.2.

15. An isolated antibody that binds to a polypeptide of either claim 13 or 14.

16. The antibody of claim 14 wherein said antibody is a monoclonal or polyclonal antibody.

17. A method of identifying an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2 comprising the steps of: exposing cells which express the nucleic acid to the agent; and determining whether the agent modulates expression of said nucleic acid, thereby identifying an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2.

18. A method of identifying an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2 comprising the steps of: -30- exposing cells which express the protein to the agent; determining whether the agent modulates at least on activity of said protein, thereby identifying an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2.

19. The method of claim 19, wherein the agent modulates the ability of the protein to phosphorylate a substrate.

20. A method of identifying binding partners for a protein comprising the sequence of SEQ ID No. 2, comprising the steps of: exposing said protein to a potential binding partner; and determining if the potential binding partner binds to said protein, thereby identifying binding partners for a protein comprising the sequence of SEQ ID No. 2.

21. A method of modulating the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2 comprising the step of:

administering an effective amount of an agent which modulates the expression of a nucleic acid encoding the protein having the sequence of SEQ ID No.2.

22. A method of modulating at least one activity of a protein comprising the sequence of SEQ ID No.2 comprising the step of: administering an effective amount of an agent which modulates at least one activity of a protein comprising the sequence of SEQ ID No.2.